network will not work

[Rick Garland]

Hi all:

RHEL4 U4 on ProLiant DL360 G5

The OS loaded fine without troubles, the startup says "bring up eth0 - success" but still unable to connect to the system.

Unable to ping the gateway but can ping the localhost

Checked the /etc/sysconfig/network-scripts and looks OK.

Where else could I look?

Thanks

[Ivan Ferreira]

Ensure that iptables is stopped:

service iptables stop

Check that the network link is detected:

ethtool eth0

Ensure that you receive packets, check RX OK from the output of:

ifconfig
netstat -ni

[Steven E. Protter]

Shalom Rick,

iptables is a good start, but if things were set right the system should still be on the network.

1) More basic, check the link light. If its not on, check the switch if its on move down this list.

2) On another machien check the arp table with the arp command. See if somone is on the network with the same ip address.

3) ping -b broadcast address see whats out there.

4) Try setting up eth1, maybe eth0 is bad.

I'll post back when I'm awake and something normal comes to mind.

SEP

[Alexander Chuzhoy]

Hi Rick,
if the network card wasn't configured as DHCP client, then "bring up eth0" doesn't necessarily means that it's IP resides in apropriate LAN. Unless you've found the solution already you can post the /etc/sysconfig/network and /etc/sysconfig/network-scripts/ifcfg-eth{0,1} and the output of ethtool eth0 and ethtool eth1.
One more thing to try-replace the network cable.

[Al Licause]

If this system has more than one network card, make sure that your network cable is plugged into what you think is eth0.

You'd be surprised at how many customers make this mistake. And with linux and the methods it uses to discover network devices, what you think is eth0 may not be......or it can move from boot to boot.

[timmy2006]

1. check cable (light or flashing)
2. ifconfig -a (check if iface is up)
3. try ping locally not 'localhost', but your machine ip on eth0\1\2.
try manually:
A) /etc/init.d/network stop
(imho i was a bad idea to start\stop net from init.d)

B) /etc/init.d/iptables stop (or any kind of FW you are using)


C) /sbin/ifconfig eth0 IP_ADDR netmask NET_MASK broadcast BCAST up

D) use tcpdump after that to listen for packets.

[Alpha977]

Hello!

try to shut-down all iptables rules on both eth and try if the machine is reachable from another machine.

Also, use a sniffer like "tcpdump" or "ethereal" on linux and another machine to see the inbound-outbound traffic.